There are several kinds of "hold-to-light" cards; the type illutrated here are maybe the most impressive though you need a strong backlight to get the full effect. Subjects are classical statues (one is illustrated in the
article in TPA), stars of the time in statue form (as the first example card) or buildings in the above areas (second example). As well as cards bearing the legend as in the heading (the second example), there are cards with this plus the name of another publisher (eg A Socki Wien), cards like the first example with just a logo, and cards bearing no legend at all. The similarity of detail including the kinds of borders on some of the cards, the dates and and the likely complexity of the manufacturing make it likely that the cards were all actually made by the same firm. As Kunstanstalt "Kosmos" also produced non hold-to-light cards, that firm may be just one of the publishers commissioning hold--to-light cards from the actual manufacturer.
Example 1 in normal light
Example 1 held in front of a strong light
Example 2 in normal light
Example 2, middle section backlit
Example 3 in normal light
Example 3 backlit